Flexible polymer film forming compositions



United States Patent 3,388,088 FLEXFIBLE PGLYMER FELM FGRMHNGCOMPOdiTiONS Paul R. Graham and August F. Gttinger, St. Louis, Mo.,

assignors to Monsanto Company, St. Louis, Mo a corporation of DelawareN0 Drawing. Filed Dec. 7, 1965, Ser. No. 512,214

6 Claims. (Cl. 26t)--32.6)

ABSTRACT OF THE DZSCLQSURE This invention relates to flexible polymerfilm forming compositions comprising (i) a polymer of polymerizablevinyl compounds and a polycarboxylic acid, (2) a deliquescentplasticizer and (3) a hydratable compound.

This invention relates to Water dispersible, polymer compositions andformulations of interpolymers of polymerizable vinyl compounds anddicarboxylic acid anhydrides having ethylenic unsaturation. it alsorelates to dry free-flowing solid formulations and compositions of saidpolymers and to films and coated products made therefrom.

It is known that certain copolymers of polymerizable vinyl compounds andalpha,beta-olefinically unsaturated polycarboxylic acids or anhydridesthereof such as styrene/maleic copolymers are soluble in water in thesalt form, such as in the ammonium salt form, and that the dissolvedpolymer solution of such polymer can be spread on a suitable substratesurface to form a film of polymer which when dried has good solvent,wax, oil and Water holdout properties.

However, such dried polymer films are brittle, and are particularly notsuitable for various industrial applications such as when applied topaper Webs and paper boards which are thereafter calendered, and used inmaking reproduction papers, or creased, crumbled or bent into suitableform for use as (a) packaging material. When subjected to such physicaltreatment these films, either as the polymer film alone or as a coatingor as an impregnating resin applied to a suitable cellulosic substratefail to pass flexibility and compressibility tests and fail holdoutproperty tests required of (b) good organic solvent, wax or oil typeholdout papers.

An object of this invention is to provide an economical polymercomposition which can be handled in dry as well as in solution form tomake polymer films therefrom having improved flexibility andcompressibility characteristics and which can be subjected to variousindustrial pressing, bending, and creasing operations and still maintainitself as a continuous film or web so as to properly function as aholdout coating or impregnant.

A further object is to provide a dry polymer formulation which can beeasily packaged, transported, and then readily dispersed in aqueousmedia for making films and coatings, therefrom.

A further object is to provide a method for forming, flexible polymerfilm forming compositions which have improved resistance to rupture orcracking caused by applied pressure in the form of calender rolls, aswell as bending, creasing, and crumbling operationsv A further object ofthis invention is to provide paper webs and paper board coated andimpregnated with polymer films which have increased flexibility andcompressibility properties.

Other objects, advantages, and aspects of this inventions will appear asthe description of this invention proceeds.

The several aspects and objects of the invention may be described,briefly, as involving a combination of (l) "ice a polymer of apolymerizable vinyl compound monomer and an olefinically unsaturatedmono-, di-, or tricarboxylic acid anhydride or a salt, amide, imide,amide-salt or ester derivative thereof in major proportion, and minorproportions, relative to the amount of the polymer, of (2) adeliquescent plasticizer such as urea, melamine, or derivatives thereofetc. and (3) a hydratable compound. The three components may be blendedin suitable proportions in a dry, solid form and packaged andtransported as such or the three components may be mixed dry or insolution form. The solution of the three ingredients, which ispreferably aqueous, can be spread on a suitable surface and dried toform a film of flexible polymer or the solution can be applied to asuitable substrate such as paper, wood, cloth, or metal to effect acoating or impregnation thereof with the polymer solution. Uponevaporating the water therefrom there remains a coated or impregnatedarticle having a flexible continuous coatingor web of polymer which maybe subjected to various handling operations.

A preferred example of a dry polymer composition of this invention isone which contains a major proportion of a styrene/maleic anhydridecopolymer, from 10 to 30 parts of urea, based on parts of the polymer,and from 5 to about 20 parts, based on 100 parts of urea, of ahydratable salt such as magnesium chloride.

These compositions may be dispersed in water with the of a basicmaterial, if the polymer is the anhydride, to any desired concentration.For film forming applications it may be desired to form aqueouscompositions containing from 20 to 50 Weight percent of the total drysolids three component polymer composition. When the polymer compositionis to be applied to a paper web or sheet or a paper board aqueoussolutions of from 5 to about 20 weight percent, based on the totalsolution, are preferred. However, aqueous polymer dispersions containingfrom about 0.5 to about 50% by Weight of these compositions are usefulfor various applications.

In addition to using the compositions in dispersed for-m mixed withwater or other easily volatilized solvent such as lower alkanols, e.g.methanol, ethanol, propanol, butanol or hydrocarbons such as pentanes,hexanes, etheralcohols such as methoxycarbitol, butoxyethanol, etc.,either alone or mixed with water, the compositions may also be used asmodifiers for starch and modified starch materials which have Wideutility in various industrial applications, but particularly in papersurface-size applications.

The interpolymers employed in the compositions of this invention may beprepared from a variety of one or more vinyl compounds and dicarboxylicor tricarboxylic acid anhydrides in a variety of ways. The term vinylcompound as used herein as describing a moiety of the interpolymercomponent of the compositions of this invention is intended to includeany polymerizable compound having a group and containing not more thanabout 20 carbon atoms. Included are the aliphatic and aromaticalphaolefin hydrocarbons such as the alkenes, e.g., ethylene, propylene,branched and straight chained butenes, hexenes, such as3-methyl-l-pentene, and isomers thereof, l-hexene, l-octene, l-nonene,l-decene, tridecene, octadecene, etc., and monocyclic aromatichydrocarbon alphaolefins such as styrene, mand p-vinyltoluene, andmixtures thereof, p-chlorostyrene, as well as lower alkenyl esters ofalkanoic and alkenoic acids such as vinyl acetate, allyl propionate,vinyl and allyl esters of acids such as decanoic, dodecanoic,tridecanoic, tetradecanoic, hexadecanoic, hetadecanoic, heptadecanoic,heptadecandienoic acid formed synthetically or derived from naturallyoccurring oils such as linseed oil, cottonseed oil, castor oil, oliveoil, safilower oil, palm oil, coconut oil, soybean oil, which aredesignated as glyceride oils, and the fatty acids found in suchnonglyceride sources as tall oil and the like; the alkyl vinyl etherssuch as the methyl, propyl, pentyl, hexyl, octyl, decyl, tridecyl,hexadecyl, and octadecyl vinyl others as well as higher alkenyl vinylethers such as tridecenyl vinyl ether, hetadecenyl vinyl ether, andother vinyl compounds described for example in Voss Patent 2,047,398. Apreferred class of vinyl compounds are those having the structuralformula where R is phenyl or a methylor chloro-substituted phenylradical or a straight or branched alkyl group having from 4 to about 12carbon atoms such as hexene, octene, decene, dodecene, tetradecene.Styrene is the preferred vinyl compound because of its availability andlow cost and because it polymerizes easily with dicarboxylic anhydridessuch as maleic anhydride to form low color interpolymers which areobtainable in dry, solid form and which are soluble in a relativelylarge variety of organic liquids.

Vinyl compounds such as acrylonitrile, acrylic acid, methacrylic acid,and alkyl acrylates and trnethacrylates such as ethyl acrylate, methylmethacrylate, vinyl chloride, vinyl alcohol, vinyl ether derivativessuch as decyl vinyl ether and vinylidene compounds such as vinylidenechloride may be used in the interpolymerization to replace a part of theabove described vinyl compounds and to modify the properties of theinterpolymer product prepared from the above described vinyl compounds.

Polycarboxylic anhydrides as used herein refers to anhydrides of diandtricarboxylic acids having from 4 to 8 carbon atoms. Examples of suchanhydride monomers which may be used include maleic anhydri.e,chloromaleic anhydride, citraconic anhydride, itaconic anhydride,acouitic anhydride, and the like. Such polycarboxylic anhydrides maycontain substituent groups such as halides, alkyl groups and the likeand at least 4 but not more than 8 carbon atoms. However, they shouldnot contain reactive substituent groups such as sulfonic acid, nitrile,or other reactive groups. Small amounts of polymerizable acids such asmaleic acid, furnaric acid, citraconic acid, itaconic acid, and alkylhalf esters of such acids such as methyl acid maleate, ethyl acidfumarate, or acrylic acid, or methyl methacrylates may be used with theanhydrides. Of course mixtures of anhydrides can be used. Maleicanhydride is preferred because of low cost and ready availability, andbecause it gives with styrene a good film forming polymer having manydesirable properties.

The interpolymers employed in this invention are suitably prepared by avariety of well known methods. The procedures can be adapted to preparethe interpolymers having molecular weights ranging from about 25,000 toabout 200,000 depending upon the vinyl monomers used. The interpolymersused usually are prepared so as to contain essentially equimolarproportions of the vinyl compound and the polycarboxylic anhydride.However, interpolymers in which the molar ratio of the dicarboxylicanhydride to the vinyl compounds is from about 0.90:1 to about 1.811 canbe utilized. The better interpolymers are prepared so as to havesubstantially alternating polycarboxylic anhydride-vinyl compoundmoieties. The interpolymers are prepared with or without solvents suchas benzene or xylene and using catalysts such asazobis(isobutyronitrile), di-tert-butyl peroxide, tert-butylperbenzoate, or any initiator which will be effective at from about50-150 C. such as isopropyl peroxydicarbonate, tetrachlorobenzoyiperoxide and the like. Molecules of excessive size introduce operationaldiii'iculties such as a rapidly increasing tendency to gel, reduced easeof application, and the like, and therefore for most combinations ofmonomers and applications it is preferred that the molecular weight ofthe interpolymer be below about 150,000. However, in some applicationshigher M.W. would be desirable. The interpolymer product is usuallyobtained as a viscous liquid at the temperature of reaction which uponcooling solidifies to a glassy solid which is easily broken up intoparticles of suitable size. If desired the polymer containing anhydridegroups therein may be treated with a base to form salts thereof,preferably an alkali metal or alkaline earth metal base such as sodiumhydroxide, potassium hydroxide, calcium hydroxide, etc. or with ammonia,or ammonium hydroxide to effect formation of the water soluble salt orhalfamide half-ammonium salt form of the copolymer. If desired thecoplymer may also be treated with alkonals such as methanol, butanol, orthe higher alkanols such as octanol, decanol, dodecanol, tetradecanol,octadecanol, as well as mixed alcohols, e.g., a mixture of alkanolshaving an average of from about 14 to 18 carbon atoms per molecule, toeffect at least partial esteriiication of the carboxyl group content ofthese copolymers. The copolymer in any of these forms may be used as acomponent of the composition of this invention.

Urea is preferred as deliquescent plasticizer of the composition of thisinvention because of its substantial solubility in water at mosttemperatures. However, melamine or its derivatives may readily be usedby dissolving the composition containing it in warm or hot water beforeforming a film or applying it in a cellulosic substrate.

The preferred urea component may be used in admixture with or may bereplaced by one or more urea derivatives or related deliquescentcompounds which serve the same function of softening the vinylcompound/polycarboxylic anhydride polymer film or coating. Thus, theterm urea as used herein is intended to include urea dimers and trimerssuch as biuret and triuret, urea salts such as urea nitrate, ureaphosphate, urea peroxide, urea oxalate, urea calcium chloride (afenil),organic group substituted ureas suchv as dialkylurea, e.g. dimethylurea, diethylurea, diarylureas such as diphenylurea, ditolvlurea,dicycloakylureas such as dicychlohexylurea as well as the melmaine typeof triazine compounds including monomeric melamine, melan, melem,dicyandiamide, dicyandiamidiuaetc. Commercial mixtures of varioustriazines or mixtures of various triazines with other amino compoundsmay be used. An example of a commercial mixture which may be used is theproduct obtained by heating dicyandiamide suificiently to obtain asignificant amount of melamine therein together with other aminocompounds.

The hydratable compound used as component 3 of the compositions of thisinvention is one which. already has or one which will take up water ofhydration when placed in an aqueous environment and which will retain atleast a portion of the water of hydration when the polymer compositioncontaining it is spread as a film or is part of a coating composition.For reasons of economy the preferred hydratable compounds used in thisinvention are hydratable salts of an anion derived from an inorganicacid and a cation derived from an alkali metal or alkaline earth metalbase. It is to be understood, however, that the used hydratable compoundin this invention is not limited to inorganic salts, but may alsoinclude other hydratable compounds such as hydratable inorganic basessuch as potassium hydroxide, lithium oxide, sodium hydroxide, etc. saltsof organic acids such as potassium and sodium salts of citric, acetic,tartaric, benzonic acids, etc. Any particular hydratable compound chosenfor use in these compositions will depend upon the use intended for thepolymer composition product, the method by which the components arecompounded, and the economics involved. Although any alkali or alkalineearth metal salt (including magnesium) of an inorganic acid may be used,as a practical matter only the more economical salts are used. Thus, thesodium and potassium, ammonium, cal cium and magnesium salts, eitheralone or mixed salts of inorganic acids of chlorine such as hydrochloricand chloridic acids, of sulfur such as sulfuric, sulfurous, sulfonic,etc. of phosphorus such as phosphoric, phosphonic, phosphinic,phosphorous, phosphonous, phosphinous, of

water complex, acts as a plasticizer or softening agent for the polymercomponent. It the urea is in the system without the hydratable salt, itwill soon lose its water through evaporation at low humidities and willcrystallize and not boron such as boric, boronic, borinic acids, as wellas function as a plasticizer. On the other hand, the hydrahydratablesalts of silicon and selenium acids may be table compound, being stablewhen hydrated is an aqueous used. Generally, any salt or base of aninorganic cation environment and will tend to replenish its water ofcrystaland an inorganic or organic anion which can exist in the lizationfrom the atmosphere as it is being dehydrated by hydrated state may beused and such materials are readily the urea component. The urea-watercomplex is probably found in various chemical handbooks, such asHandbook 10 polymeric and acts as an excellent plasticizer for polymersof Chemistry by Norbert A. Lange, Ninth edition, pubof vinyl compoundsand olefinically unsaturated polycarlished by Handbook Publishes, Inc.,Sandusky, Ohio, boxylic monomers such as styrene/maleic anhydride, acid,U.S.A., 1956, pages 214 to 333. Examples of the more salt, amide-salt,and ester copolymers and other polar practical economical salts whichmay be used include materials.

aluminum chloride, hydrated alumina, aluminum sulfate, In addition tothe above stated advantages of this inaluminum ammonium sulfate,ammonium acid phosphite, vention the application of these polymer,dcliquescent antimony trichloride, borium citrate, cadmium nitrate,plasticizer, and hydratable salt formulations of this invencalciumacetate, calcium ammonium phosphate, calcium tion to cellulosicsubstrates provides coated paper procitrate, calcium metaborate, calciumbenzoate, calcium ducts having improved non-polar solvent holdproperties. hypochlorite, calcium lactate, calcium nitrate, calcium Theinvention is further illustrated by the following oxalate, calciumthiosulfate, ferric ammonium oxalate, examples which illustrate theenhanced flexibility and ferric chloride, ferric nitrate, ferricpyrophosphate, ferric compressibility of polymer film formulations ofthis insulfate, magnesium acetate, magnesium ammonium sulvention.

fate, magnesium benzoate, magnesium metaborate, mag- Example 1 nesiumcitrate, magnesium chlorate, magnesium potas- Three dry free-flowingpolymer compositions were com sium chloride, nickel ammonium chloride,nickel ampounded and then dissolved in water to provide solutions moniumsulfate, nickel chloride, nickel ferrocyanide, having about 10 percenttotal solids content. The three nickel sulfate, potassium tetraborate,potassium carbonate, compositions were:

potassium hydrosulfide, potassium hydroxide, sodium car- (1) 10 parts ofa commercially available dry, free-flowbonate, sodium tetraborate,sodium sesquicarbonate, soing disodium salt of a styrene/maleicanhydride copolydium citrate, sodium dithionate, sodium ferric oxalate,mer having a viscosity of about 40 centipoises in a 3% sodium hydroxide,borax, sodium hypophosphate, sodium polymer solids solution in water at25 C.

oxide, sodium perborate, sodium peroxide, sodium phos- (2) 8.4 parts ofthe same styrene/maleic disodium salt phate, sodium metasilicate, sodiumsulfate, sodium sulfide, polymer as in (1) above, and 1. 68 part-s solidurea. sodium tartarate, titanium oxalate, zinc acetate, zinc am- (3) 8.4par-ts of the same polymer as in (1) above, monium sulfate, zincchloride, zinc chlorate, zinc dithio- 1.68 parts :of urea, and 0.336part of magnesium chlonate, zinc nitrate, etc. ride *hex'ahydrate.

We have not established the mechanism by which the The three dryformulations were then dissolved in compositions of this inventionaffect their better properties sufficient water to provide solutionshaving about 10% but we believe that the following explanation is atleast 40 total solids content. The viscosity and pH properties of thepossible. resulting solutions, the properties of films cast from the Thehydratable compound acts as a water donor to the respective solutions,and compressibilities of papers coated urea or other deliquescentplasticier component which with the respective polymer solutions aregiven in the when in the presence of this water, possibly as aureafollowing table.

TABLE I Polymer Formulation No.

Solution:

Total Solids Content,

percent 10. 0 10. 08 10. 42 Viscosity at C. 42. 8 37. 2 30. 8 pH 7.5 7.17.68 Cast Film-Flexibility at:

70 F, RH! Brittle a 76 F, 38% RH Brittle Brittle Flexible 2Compressibility oi Coated Paper -Solvent Holdout (number ofpenetrations):

Uncal. Cal. Uncal. Cal. Uncal. Cal.

After 24 hours at 71 F.,

64% RH 28 50+ 11 2s a 6 After 24 hours at F.,

55% RH 30 50+ 10 20 5 8 After 24 hours at 71 F 1 RH means RelativeHumidity. 2 Film sample could be bent without breaking. a In this testcoated paper samples were exposed to the enumerated temperature,relative groups are present, and which has a boiling point ranging from182.5 C. (first drop of distillate) to 211.4" 0. (dry point).

4 Some Flexibility.

6 Very Flexible.

What is claimed is:

1. A composition comprising (a) a Water soluble polymer of apolymerizable vinyl compound and an olefinically unsaturatedpolycarboxylic acid anhydride, selected from the group consisting ofdicarboxylic acid anhydrides and tricarboxylic acid anhydrides havingfrom 4 to 8 carbon atoms, wherein the molar ratio of the polycarboxylicacid anhydride to the vinyl compound is from about 0.90:1 to about 1.8to 1, and minor proportions relative to the weight of component (a) of(b) 21 deliquescent plasticizer wherein said plasticizer is an organicamine selected from the group consisting of urea, melamine, and mixturesand derivatives thereof, and (c) an hydratable compound.

2. A composition as described in claim 1 wherein in the polymer (a) thepolymerizable vinyl compound moiety is a vinyl monocylic aromatichydrocarbon having from 8 to 10 carbon atoms, and the olefinicallyunsaturated polycarboxylic acid anhydride is maleic anhydride, thedeliquescent pl-asticizer (b) is an organic amine selected from thegroup consisting of urea, melamine, and mixtures and derivatives thereofand the hydratable compound is a salt :of an inorganic acid :anion andthe cation is selected from the group consisting of alkali and alkalineearth metals.

3. -A composition as described in claim 2 wherein the polymer (a) is apolymer of styrene and maleic anhydride, component (b) is urea, andcomponent (c) is magnesium chloride.

4. A dry, free-flowing solid composition comprising a major proportionof (a) a dry water soluble styrene/ maleic anhydride polymer, having amolar ratio of maleic anhydride to styrene of from about 0.90:1 to about1.8

to 1, and minor proportions of (b) solid urea, and (c) a solid magnesiumchloride salt.

5. A paper web treated with an aqueous composition comprising waterhaving dispersed therein (a) a water soluble polymer of :a polymerizablevinyl compound and an olefinically unsaturated polycarboxylic acidanhydride, selected from the group consisting of dicarboxylic acidanhydrides and tricarboxylic acid anhydrides having from 4 to 8 carbonatoms, wherein the molar ratio of the polycarboxylic acid anhydride tothe vinyl compound is from about 0.90:1 to about 1.8 to 1, and minorproportions relative to the amount of the polymer (a) of (b) adeliquescent plasticizer wherein said placticizer is an organic amineselected from the group consisting of urea, melamine and mixtures andderivatives thereof, and (c) a liydratable compound, and dried to obtaina web having improved holdout properties.

6. A coated paper web having improved holdout properties comprising ace'llulosic paper Web having applied to at least one surface thereof anaqueous composition containing (a) a Water soluble styrene/maleicc-opolymer having a molar ratio of maleic anhydride to styrene of fromabout 0.90:1 to about =1.8 to 1, (b) urea, and (c) a magnesium chloridesalt, and dried to remove dispersing water therefrom.

References Cited UNITED STATES PATENTS 2,607,762 8/ 19521 Bowen 260-78.52,723,195 11/1955 Blake 26078.5

MORRIS LIEBMAN, Primary Examiner.

S. L. FOX, Assistant Examiner.

